• Nuclear Engineering and Technology
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• v.19 no.2
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• pp.77-84
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• 1987

Statistical evaluation for the heat transfer correlation in the containment subcompartments is carried out from HDR experimental data. Heat transfer data for three HDR blowdown tests, V.42, V.43 and V.44, are analyzed to deduce the correlation. As Uchida already proposed, air-to-steam density ratio is proven to be the most affecting parameter in this study. Here Uchida heat transfer correlation is revised by including temperature difference between the atmosphere and the wall surface, and atmospheric pressure. In addition to these dependencies, atmospheric turbulence and time factor may be included in the model. This implication, however, is not successful, because turbulence and transient phenomena were not adequately quantified in the HDR program. It is concluded that a strong correlation exists between the heat transfer coefficient and temperature differences, specially for forced circulation conditions.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.292-295
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• 2008

In a SCWR (SuperCritical pressure Water cooled Reactor), the coolant temperature initially at below the pseudo-critical temperature at the bottom of a reactor core increases as the coolant flows upward through the sub-channels of the fuel assemblies, and it finally becomes higher than the pseudo-critical temperature when it leaves the reactor core. At certain conditions, heat transfer deterioration occurs near the pseudo-critical temperature and it may cause a drastic rise of the fuel surface temperature resulting a fuel failure. Therefore, an accurate estimation of the heat transfer coefficient is very important for the thermal-hydraulic design of a reactor core. An experiment on heat transfer to the vertically upward flowing $CO_2$ at a supercritical pressure in a circular tube were performed at KAERI. The internal diameter of the test section is 6.32 mm, which corresponds to the hydraulic diameter of a sub-channel in the conceptional design proposed by KAERI. The test range of the mass flux is 285 to 1200 kg/m$^2$s and the maximum heat flux is 170 kW/m$^2$. The inlet pressure is maintained at 8.12 MPa, which is 1.1 times the critical pressure. A new correlation, which covers both the normal and deterioration heat transfer regimes was proposed and compared with the estimations by exiting correlations.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.154-159
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• 2008

Two-phase flow boiling heat transfer of R-410A in horizontal small tubes was reported in the present experimental study. The local heat transfer coefficients were obtained over a heat flux range of 5 to 40 kW/$m^2$, a mass flux range of 170 to 600 kg/$m^2s$, a saturation temperature range of 3 to $10^{\circ}C$, and quality up to 1.0. The test section was made of stainless steel tubes with inner diameters of 0.5 and 3.0 mm, and lengths of 330 and 3000 mm, respectively. The section was heated uniformly by applying a direct electric current to the tubes. The effects on heat transfer of mass flux, heat flux, inner tube diameter, and saturation temperature were presented. The experimental heat transfer coefficient is compared with six existing heat transfer coefficient correlations. A new boiling heat transfer coefficient correlation based on the superposition model for R-410A in small tubes was developed with mean deviation of 10.13%.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.4
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• pp.36-42
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• 1996

Analysis of heat transfer on small-size Diesel engine is required for the development of high performance and efficiency engine. This basic study aims to establish heat transfer technique for marine Diesel engine. The main results from this study are as follows : 1) Overall engine heat transfer correlation of Re-Nu. 2) Radiant heat flux as fraction of total heat flux over the load range of several different Diesel engine. 3) Characteristics of heating curves on piston, cylinder liner and head. 4) Surface heat flux versus injection timing.

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1630-1639
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• 2004

The present paper investigated the correlation between the acoustic pressure variations and the augmentation of heat transfer in the ultrasonic induced acoustic fields. The augmentation ratios of heat transfer coefficient were experimentally measured and were compared with the profile of the pressure distribution in the acoustic fields predicted by numerical analysis. For numerical analysis, a coupled finite element-boundary element method (coupled FE-BEM) was applied. The results of the present study reveal that the acoustic pressure is higher near two ultrasonic transducers than other points where no ultrasonic transducer was installed. The augmentation trend of heat transfer is similar with the profile of the acoustic pressure distribution. In other words, as the acoustic pressure increases, the higher augmentation ratio of heat transfer is obtained. Numerical and experimental studies clearly show that the acoustic pressure variations are closely related to the augmentation of heat transfer in the acoustic fields.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.05a
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• pp.134-139
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• 2000

Evaporating heat transfer characteristics of R-22 were measured inside smooth horizontal copper tubes with inner diameters of 3.36 mm and 5.35 mm respectively. The experiments were conducted in the closed loop which was driven by a magnetic gear pump. Experiments were performed for the following range of variables ; mass velocity of refrigerants (200 to 400 $kg/m^2$ .s) saturation temperature ($0^{\circ}C, \; 5^{\circC$}) and quality (0 to 1.0) The main results obtained are as follows : Evaporating heat transfer coefficients in the small diameter tubes (ID<7 mm) were observed to be strongly affected by a variety of diameters and to differ from those in the large diameter tubes. The heat transfer coefficients of the small diameter tubes are higher than those of the large diameter tubes. Comparing the heat transfer coefficients between experimental results and some well-known previous predictions (Shah's correlation Gungor-Winterton's and Kandlikar's correlation) it was very difficult to apply those to small diameter tubes.

• International Journal of Air-Conditioning and Refrigeration
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• v.15 no.4
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• pp.163-168
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• 2007

The feature of six existing condensation heat transfer correlations for microfin tubes were evaluated with the consideration of vapor quality, mass flux, geometries, and various refrigerants. The Kosky and Staub [15] and the Jaster and Kosky [16] correlations for smooth tube were used for the evaluation of the heat transfer enhancement factor (EF). For the prediction of zeotropic mixtures, most correlations show discrepancy with previous measurements. The Yu and Koyama [4] and the Shikazono et al. [8] correlations do not consider spiral angle effect. The Han and Lee [10] correlation shows fin height growth deteriorates heat transfer. Experimental verification to develop reliable condensation heat transfer correlation for microfin tubes is still needed with the consideration of geometrical effects and working conditions.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.3
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• pp.224-234
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• 2007

Large diameter tubes have been used until comparatively lately. However, small diameter tubes are largely used because of their high efficiency in heat transfer and low cost, recently. This study focuses on the experimental research of the heat transfer coefficients during evaporation process of R-22 and R-134a in small diameter tubes. The evaporation heat transfer coefficients were measured in smooth horizontal copper tubes with ID 1.77, 3.36 and 5.35 mm. The evaporation heat transfer coefficients in the small diameter tubes (ID <7 mm) were observed to be strongly affected by the size of tube diameters and to differ from those of general predictions in the large diameter tubes. The heat transfer coefficients of ID 1.77 mm copper tube were higher by 20 and 30 % than those of ID 3.36 mm, ID 5.35 mm copper tubes respectively. Also, it was found that it was very difficult to apply some well-known previous predictions (Shah's, Jung's. Kandlikar's and Oh-Katsuda's correlation) to small diameter tubes. Based on the data, the new correlation is proposed to predict the evaporation heat transfer coefficients of R-22 and R-134a in small diameter tubes.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1119-1122
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• 2009

The use of cooling towers in the air conditioning systems of buildings is increasing. In closed wet cooling towers, the heat transfer between the air and surface tubes can be composed of the sensible heat transfer and the latent heat transfer. The latent heat transfer is affected by the air and spray water. This study provides a designing methodology of heat exchanger for closed wet cooling tower. The correlation equation was derived to interpret the mass transfer coefficient based on the analogy of the heat and mass transfer and the experimental results. The results from this correlation equation showed fairly good agreement with experimental data.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.68-73
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• 2006

The present paper deals with an experimental study of boiling heat transfer characteristics of R-290, and is focused on pressure gradient and heat transfer coefficient of the refrigerant flow inside horizontal smooth minichannel with inner diameter of 3.0 mm and length of 2000 mm. The direct heating method applied for supplying heat to the refrigerant where the test tube was uniformly heated by electric current which was applied to the tube wall. The experiments were conducted with R-290 with purity of 99.99% at saturation temperature of 0 to $10^{\circ}C$. The range of mass flux is $50{\sim}250kg/m^2s$ and heat flux is $5{\sim}20kW/m^2$. The heat transfer coefficients of R-290 increases with increasing mass flux and saturation temperature, wherein the effect of mass flux is higher than that of the saturation temperature, whereas the heat flux has a low effect on increasing heat transfer coefficient. The significant effect of mass flux on heat transfer coefficient is shown at high quality, the effect of heat flux on heat transfer coefficient at low quality shows a domination of nucleate boiling contribution. The heat transfer coefficient of the experimental result was compared with six existing heat transfer coefficient correlation. Zang et al.'s correlation(2004) gave the best prediction of heat transfer coefficient.